On the in vivo origin of human nasal mesenchymal stem cell cultures

OBJECTIVES: Mesenchymal stem cells (MSCs), classically expanded in culture from bone marrow, are of broad interest to the regenerative medicine community. Human nasal turbinate mesenchymal‐like stem cell cultures have also been described, defined by an in vitro phenotype similar to bone marrow MSCs. Nonetheless, the identity in vivo of the cells that give rise to nasal MSC‐like cultures remains unclear, and these cells are often suggested to be related to olfactory lineages. Here, we sought to define the in vivo phenotype of human nasal MSC‐like cells. METHODS: Human turbinate tissue samples were used for RNA and immunohistochemical analysis. We also analyzed a recently published single cell RNA‐sequencing dataset from adult human olfactory and respiratory mucosa samples from our lab, to focus on cell populations expressing MSC markers. Immunochemistry was performed to stain turbinate sections and nasal MSC cultures for selected markers. RESULTS: While there is no single MSC‐specific gene, we identified a human nasal mucosal cell population in vivo that uniquely expressed transcripts characteristic of typical MSC cultures, including ENG (CD105), NES, and CD34, and lacked expression of other transcripts associated with surface epithelia. The expression of transcription factors such as SOX17, EBF1, and FOXP1 suggests cells in the MSC‐like cluster maintain an ability to direct cell fate, consistent with the behavior of nasal MSC‐like cells in vitro. SOX17 was found to be uniformly expressed by nasal MSC cultures, consistent with the in vivo data. Immunohistochemistry of human nasal tissue samples indicated that ENG, CD34, and SOX17 expression localized selectively to cells surrounding blood vessels in the lamina propria. CONCLUSION: Our findings provide evidence that the in vivo origin of nasal MSC‐like cultures is likely a vascular or pericyte population, rather than cells related to the olfactory neuronal lineage. LEVEL OF EVIDENCE: NA.